1. Field of the Invention
The present invention relates to a method of stopping an industrial robot after the industrial robot collides with an object, and more particularly to a method of stopping an industrial robot for increased safety.
2. Description of the Related Art
When an industrial robot (hereinafter referred to as a "robot") collides with foreign matter due to a teaching process error or the like, it is necessary to stop the operation of the robot for the safety of the operator and the protection of the robot. It is customary to apply a speed command of nil to the servomotor associated with each axis with respect to which the collision has been detected, thereby producing a reverse torque to stop the operation of the robot in as short a period of time as possible. For an axis with respect to which no collision is detected, an alarm is issued after a position deviation or error, which is the difference between a position command for the servomotor and an actual position thereof, takes a value greater than a predetermined value, thus cutting off the drive current supplied to the servomotor.
According to the above conventional process, since a collision is detected with respect to each axis, and a reverse torque is applied to any axis with respect to which a collision is detected, the operation of the axis is stopped in a short period of time. For an axis with respect to which no collision is detected, however, its operation based on a motion command is continued until the position command for the axis exceeds a predetermined value and an alarm is issued. Therefore, the robot moves along a path different from a taught path, resulting in a safety failure. Inasmuch as the de-energization of the servomotor for the axis with respect to which no collision is detected is delayed, the complete stoppage of the robot is also delayed.